急速な視力視野障害で発症した中頭蓋窩くも膜囊胞の1例

Acute Onset of Visual Disturbance in a Patient with Arachnoid Cyst in the Middle Cranial Fossa

はじめに

　中頭蓋窩くも膜囊胞は，頭蓋内くも膜囊胞の発生部位として最も多く，頭蓋骨変形のみで無症状のものも多い。症候性のものでは頭蓋内圧亢進症状，てんかん発作にて発症することが多いが，ときに囊胞が圧迫効果を示し，巣症状をきたすこともある^1，2）。

　われわれは，急速な一側の視力低下で発症した中頭蓋窩くも膜囊胞に対し，緊急に囊胞開放術を施行し，視力がほぼ改善した症例を経験した。視神経圧迫を呈した例の報告は過去になく，中頭蓋窩くも膜囊胞による脳神経症状と，くも膜囊胞の増大した機序について文献的考察を加え報告する。

Abstract

　Intracranial arachnoid cyst occurs most frequently in the middle fossa.　Most of them are asymptomatic with or without neurological involvement.　However some develop neurological deficits such as increased intracranial pressure, which manifests as headache, epilepsy and focal neurological deficits.　Here we present an adult case of arachnoid cyst in the middle cranial fossa: the patient demonstrated rapidly deteriorating visual field defect and decreased visual acuity.　The symptoms were improved by an emergency surgery.　This is the first case report describing optic nerve compression due to an arachnoid cyst.　Result of the coronal and sagittal magnetic resonance imaging (MRI) scans showed effective optic nerve compression.　Long-standing asymptomatic arachnoid cysts might progress rapidly to cause cranial nerve deficits thus meticulous MRI follow-up are important in these patients.

(Received: April 25, 2007, Accepted: August 17, 2007)